Rossby wave instability

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Rossby Wave Instability (RWI) is a concept related to astrophysical accretion discs. In non-self-gravitating discs, for example around newly forming stars, the instability can be triggered by an axisymmetric bump, at some radius ${\displaystyle r_{0}}$, in the disc surface mass-density. It gives rise to exponentially growing non-axisymmetric perturbation in the vicinity of ${\displaystyle r_{0}}$ consisting of anticyclonic vortices. These vortices are regions of high pressure and consequently act to trap dust particles which in turn can facilitate planetesimal growth in proto-planetary discs.^[2] The Rossby vortices in the discs around stars and black holes may cause the observed quasi-periodic modulations of the disc's thermal emission.

Rossby waves, named after Carl-Gustaf Arvid Rossby, are important in planetary atmospheres and oceans and are also known as planetary waves.^[3][4][5][6] These waves have a significant role in the transport of heat from equatorial to polar regions of the Earth. They may have a role in the formation of the long-lived (${\displaystyle >300}$ yr) Great Red Spot on Jupiter which is an anticyclonic vortex.^[7] The Rossby waves have the notable property of having the phase velocity opposite to the direction of motion of the atmosphere or disc in the comoving frame of the fluid.^[2][3]

The theory of the Rossby wave instability in accretion discs was developed by Lovelace et al.^[8] and Li et al.^[9] for thin Keplerian discs with negligible self-gravity and earlier by Lovelace and Hohlfeld^[10] for thin disc galaxies where the self-gravity may or may not be important and where the rotation is in general non-Keplerian.

The Rossby wave instability occurs because of the local wave trapping in a disc. It is related to the Papaloizou and Pringle instability;^[11][12] where the wave is trapped between the inner and outer radii of a disc or torus.

References[edit]

Further reading[edit]

• Lovelace, R V E.; Romanova, M. M. (2014). "Rossby wave instability in astrophysical discs". Fluid Dynamics Research. 46 (4): 041401. arXiv:1312.4572. Bibcode:2014FlDyR..46d1401L. doi:10.1088/0169-5983/46/4/041401. S2CID 118504602.